Presently magnetic separators may be cleaned by back-flushing through the matrix; introducing the flush fluid through the outlet at the downstream end of the matrix and recovering it at the inlet after exit from the upstream end. The flush fluid is stored in a holding tank downstream of the separator and may be either the fluid output from the separator or an externally supplied cleansing fluid. This requires an additional pipeline to interconnect the holding tank with the outlet of the separator if a separate cleaning fluid is used, or an enlarged collection pipe if the fluid collected from the separator is used for flushing. In either case the pipe requires at least two bends if, as is normally necessary, the holding tank is not to interfere with access to the separator. These bends severely reduce the energy of the flushing flow and the added length or diameter of the outlet pipe increase the apparatus cost. The high-energy fluid flow approaching the downstream end of the matrix through the outlet also requires some type of baffle in or at the outlet to distribute the flush fluid over the entire matrix area, and not just the area beneath the outlet. This further depletes the energy of the fluid at the matrix. The flushing fluid, be it externally or internally derived, is normally driven out of the holding tank and back into and through the matrix by a surge of high-pressure fluid such as air. This requires another holding tank to store the pressurized driving fluid. To improve the flushing action, air or some other fluid is distributed through the flush fluid by means of nozzles or the like in the outlet pipe to perturb the flush fluid. However, the means for distributing the perturbing agent in the outlet interferes with and further impedes the flush fluid on the way to back-flush the matrix and is relatively ineffective in mixing the perturbing agent with the flush fluid.